Since the advent of the rapid rise of the price of natural gas and fuel oil, a growing interest has developed in the use of wood as a fuel. The use of wood burning stoves and heaters has rapidly increased, and as a direct result thereof there has been a rapid increase in chimney fires and related problems. The burning of wood, as opposed to natural gas or fuel oil, generates a substantial residue that includes cresote. Typically wood burning devices have chimneys or flues that require regular maintenance, inspection, and cleaning to remove the soot and creosote. If this is not done, the chimney tends to become clogged and the cresote buildup also can catch fire.
The problem in the use of wood burning stoves has been long known, and it has been recommended that periodic inspection and maintenance of the flues or chimneys be undertaken in order to ensure safe operation of wood burning equipment. Many users of this type of equipment become lax or are unaware of the maintenance problems, and as a result thereof the use of wood burning equipment has created a substantial safety problem. In order to avoid this problem, devices have been suggested which monitor the rate of airflow through a chimney as an indication of the creosote buildup. This type of device has many drawbacks including the fact that the change of airflow can be a function of temperature, and the availability of burner air supplied to the inlet of the wood burning apparatus.